<template>
  <view class="easy-loadimage" :style="[boxStyle]" :id="uid">
    <image class="origin-img" :style="[imageRadius]" :src="imageSrc" :mode="mode" v-if="loadImg&&!isLoadError"
           v-show="showImg" :class="{'no-transition':!openTransition,'show-transition':showTransition&&openTransition}"
           @load="handleImgLoad" @error="handleImgError">
    </image>
    <view class="loadfail-img" v-else-if="isLoadError"
          :style="{'background-image': `url(${urlDomain}crmebimage/presets/loadfail.png) no-repeat center`}"></view>
    <view :class="['loading-img','spin-circle',loadingMode,mode]" v-show="!showImg&&!isLoadError"></view>
  </view>
</template>
<script>
import {
  throttle
} from '@/utils/validate.js'

// 生成全局唯一id
function generateUUID() {
  return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function (c) {
    let r = Math.random() * 16 | 0,
        v = c == 'x' ? r : (r & 0x3 | 0x8);
    return v.toString(16);
  })
}

export default {
  name: 'easyLoadimage',
  props: {
    imageSrc: {
      type: String || null,
      default() {
        return '';
      }
    },
    mode: {
      type: String,
      default: "aspectFill"
    },
    loadingMode: {
      type: String,
      default: 'looming-gray'
    },
    openTransition: {
      type: Boolean,
      default: true,
    },
    viewHeight: {
      type: Number,
      default() {
        return uni.getSystemInfoSync().windowHeight;
      }
    },
    width: {
      type: String,
      default: ''
    },
    height: {
      type: String,
      default: ''
    },
    borderRadius: {
      type: String,
      default: ''
    },
    radius: {
      type: Number,
      default: 0
    },
  },
  data() {
    const that = this;
    return {
      urlDomain: this.$Cache.get("imgHost"),
      uid: 'uid-' + generateUUID(),
      loadImg: false,
      showImg: false,
      isLoadError: false,
      borderLoaded: 0,
      showTransition: false,
      scrollFn: throttle(function () {
        // 加载img时才执行滚动监听判断是否可加载
        if (that.loadImg || that.isLoadError) return;
        const id = that.uid
        const query = uni.createSelectorQuery().in(that);
        query.select('#' + id).boundingClientRect(data => {
          if (!data) return;
          if (data.top - that.viewHeight < 0) {
            that.loadImg = !!that.imageSrc;
            that.isLoadError = !that.loadImg;
          }
        }).exec()
      }, 200)
    }
  },
  computed: {
    boxStyle() {
      return {
        width: this.width,
        height: this.height,
        borderRadius: this.radius * 2 + 'rpx'
      }
    },
    imageRadius() {
      if (this.radius && this.radius > 0) {
        return {
          'border-radius': this.radius * 2 + 'rpx'
        }
      }
    }
  },
  methods: {
    init() {
      this.$nextTick(this.onScroll)
    },
    handleBorderLoad() {
      this.borderLoaded = 1;
    },
    handleBorderError() {
      this.borderLoaded = 2;
    },
    handleImgLoad(e) {
      this.showImg = true;
      setTimeout(() => {
        this.showTransition = true
      }, 50)
    },
    handleImgError(e) {
      this.isLoadError = true;
    },
    onScroll() {
      this.scrollFn();
    },
  },
  mounted() {
    this.init()
    uni.$on('scroll', this.scrollFn);
    this.onScroll()
  },
  beforeDestroy() {
    uni.$off('scroll', this.scrollFn);
  }
}
</script>

<style scoped lang="scss">
.easy-loadimage {
  width: 100%;
  height: 100%;
  overflow: hidden;
  margin: auto;
  display: flex;
  justify-content: center;
}

.widthFix {
  min-height: 172px;
}

/* 官方优化图片tips */
image {
  will-change: transform;
  overflow: hidden;
  object-fit: cover;
}

/* 渐变过渡效果处理 */
image.origin-img {
  width: 90%;
  height: 90%;
  opacity: 0.3;
  /* max-height: 360rpx; */
  /* border-radius: 14rpx;
  overflow: hidden; */
  /* min-height: 360rpx; */
}

image.origin-img.show-transition {
  transition: opacity .5s;
  opacity: 1;
}

image.origin-img.no-transition {
  opacity: 1;
}

/* 加载失败、加载中的占位图样式控制 */
.loadfail-img {
  height: 100%;
  background-size: 50%;
}

.loading-img {
  width: 100%;
  height: 100%;
}

/* 动态灰色若隐若现 */
.looming-gray {
  animation: looming-gray 1s infinite linear;
  background-color: #e3e3e3;
}

@keyframes looming-gray {
  0% {
    background-color: #e3e3e3aa;
  }

  50% {
    background-color: #e3e3e3;
  }

  100% {
    background-color: #e3e3e3aa;
  }
}

/* 骨架屏1 */
.skeleton-1 {
  background-color: #e3e3e3;
  background-image: linear-gradient(100deg, rgba(255, 255, 255, 0), rgba(255, 255, 255, 0.2) 50%, rgba(255, 255, 255, 0) 80%);
  background-size: 100rpx 100%;
  background-repeat: repeat-y;
  background-position: 0 0;
  animation: skeleton-1 .6s infinite;
}

@keyframes skeleton-1 {
  to {
    background-position: 200% 0;
  }
}

/* 骨架屏2 */
.skeleton-2 {
  background-image: linear-gradient(-90deg, #fefefe 0%, #e6e6e6 50%, #fefefe 100%);
  background-size: 400% 400%;
  background-position: 0 0;
  animation: skeleton-2 1.2s ease-in-out infinite;
}

@keyframes skeleton-2 {
  to {
    background-position: -135% 0;
  }
}
</style>